Every 15k +-. Easy, take the plastic appearance cover off, get a big set of channel locks and put the jaws in slots and loosen. Oops, first drain the fuel bowl, little yellow lever toward the back. If you attach a hose to the tube that runs about half way down the passenger side of the engine you can catch in a can so there is no mess. Pull old filter out, there may be some resistance, just keep pulling, clean out any junk in the bottom of bowl be careful not to hurt anything in there. Install new filter with BOTH o-rings in the proper places. One is beveled and needs to go the right way. Put cap back on and thighten with same channel locks, DON'T forget to close the yellow drain thingy. Cycly key a couple of three times without starting, crank the fourth time and it should start.
Once you do one, the rest are easy.
Paul B